In Europe, about ninety percent of the population chooses cremation over burial. In the U.S., the percentage is lower, but rising each year.
The cremators currently in use include a cremation burner positioned in the primary chamber to combust the casket and remains which are supported by a hearth. The burner is fired almost continuously throughout the cremation process. The gases flow from the primary chamber to an afterburningarea where they are re-burned, and thereafter follow a predetermined path of travel to a chimney. Typically, the path of travel is a simple "U"-shaped path, i.e., the gases flow from the afterburner area at the trailing end of the hearth to the leading end of the hearth, execute a single return bend, and flow back to the trailing end of the hearth and hence to the chimney.
Perhaps the most advanced cremator of the prior art is shown in U.S. Patent No. 4,603,644 to Brookes. In the Brookes device, the hot gases follow a path of travel that begins at a primary ignition burner positioned above the horizontal hearth at a leading end thereof, and extends therefrom to a trailing end of the hearth, over an ash trough at a trailing end of the hearth, into an afterburner passageway where the gases flow downwardly to a plane below the hearth and ash trough, toward the leading end of the hearth while in said plane below said hearth, through a return bend and toward the trailing end of the hearth to a chimney. Thus, the path of travel of the gases below the hearth includes a single return bend. As a consequence, the temperature of the gases becomes increasingly difficult to maintain. Recent Environmental Protection Agency regulations require that hot gases flowing through cremators must dwell therewithin for at least a full second, at 1800 F.
In the Brookes device, and other earlier devices, the gases flowing below the hearth begin to cool as they leave the afterburner area, i.e., by the time the gases execute the return bend at the leading end of the cremator, and travel the length of the hearth and ash trough to the chimney, said gases will have cooled considerably as there are no further re-heating means.
The prior art, considered as a whole, neither teaches nor suggests how the dwell time could be increased, or how the gases could be reheated to maintain a constant ideal combustion temperature.